Support forwarding of ndjson streams

[welteki]

Description

Add support for streaming Newline Delimited JSON (NDJSON) from functions.

Additional fixes:

• Support Accept headers with multiple Accept values
• Accept header values should be matched case insensitive. As stated in RFC7321 Media Types are case-insensitive

Motivation and Context

• I have raised an issue to propose this change (required)

How Has This Been Tested?

A unit test was added.
Tested E2E with OpenFaaS Pro and a custom Go function that streams an NDJSON response.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.